358 



INDIGO. 



process of manufacture cannot possibly utilise, so that the richer the 

 plant and the more indican it contains, the greater is the waste in 

 the ordinary process. 



The indigo plant is chiefly cultivated in Bengal, in the Delta of 

 the Ganges, on those districts lying between the Hooghly and the 

 main stream of the former river. The ground is ploughed in October 

 and November, after the cessation of the rains ; the seeds are sown in 

 March and beginning of April. In July the plants are cut when in 

 blossom, that being the time when there is the greatest abundance of 

 dye-matter. 



A fresh moist soil is the best, and about 12 lb. of seed are used 

 for an acre of land. The plants are destroyed by the periodical in- 

 undations, and so last only for a single year. "When the plant is cut 

 it is first steeped in a vat till it has become macerated and parted 

 with its colouring matter ; then the liquor is let off into another vat 

 in which it undergoes a peculiar process of beating to cause the fecula 

 to separate from the water ; the fecula is then let off into a third vat, 

 where it remains some time, and is then strained through cloth bags 

 and evaporated in shallow wooden boxes placed in the shade. Before 

 it is perfectly dry, it is cut into small pieces an inch square : it is 

 then packed up for sale. Indigo, however, is one of the most pre- 

 carious of Indian crops, being liable to be destroyed by insects, as 

 well as inundation of the rivers. It is generally divided into two 

 classes, viz. the Bengal and Oude indigo. Madras indigo is not 

 much inferior to that grown in Bengal. The green leaf manufacture 

 is followed in all the indigo growing districts of the Madras Pre- 

 sidency, save the province of South Arcot. In the latter the dry leaf 

 process is still persevered in, but probably it is so only because of 

 the distance to which the leaf has generally to be cai-ried before it 

 reaches the factory, and the consequent partial drying that takes 

 place on the journey. The best indigo comes from the districts of 

 Kishnagur, Jessore, Moorshedabad, and Tirhoot. 



The fecula is much improved after being collected by being boiled 

 in coppers and then pressed into boxes. Indigo is sometimes manu- 

 factui'ed by simply collecting the fecula, and dropping it down in 

 cakes to harden in the sun ; this is termed " gaud indigo." 



Good indigo is known by its fine purple-blue colour, and by its 

 fracture ; but when exposed to the continued action of air or water, or 

 any other agents, it undergoes certain changes, which differ very 

 materially in different grades or qualities of the article, and, unless a 

 person is a good judge, he will be unable to tell the grade and quality. 

 This can only be determined by closely examining the indigo in some 

 test process. Good indigo is always very light — the lighter the 

 better — that is, the freer it is from all foreign earthy matters ; and if 

 rubbed against a white cloth it does not easily coloui' it. Another 

 sure test is its handsome copper gloss. This may have been caused 

 by the rubbing of the angles of the pieces while in transportation, or 

 it may be made by rubbing them with any hard substance. This 

 copper gloss is the consequence of the mechanical thickening of the 

 colouring matter with which indigo abounds ; in this it resembles all 

 pure coloiu'ing matters. 



One thing to be especially remarked is the fine dark colour of the 



